Upload
others
View
6
Download
0
Embed Size (px)
Citation preview
Fluid dynamic challenges of future Nano Cellulose Fiber processes
Daniel SöderbergInnventia and Royal Institute of Technology
St kh l S dStockholm, Sweden
PaperCon 2011 Page 643
Organisation of Cellulose in Fibres
fAdapted from: Rowland and Roberts (1972)
PaperCon 2011 Page 644
Microfibrillar Cellulose (MFC) Turbak and co-workers at ITT in the beginning of the 80´s
Disintegration (homogenization)
Turbak and co workers at ITT in the beginning of the 80 s
Disintegration (homogenization)
Microfibrillated Cellulose MFCTurbak A F Snyder F W and Sandberg K RTurbak, A.F., Snyder, F.W. and Sandberg, K.R.J. Appl. Polym. Science. Applied Pol. Symp. 37(1983)
PaperCon 2011 Page 645
NanoCellulose Gel (Innventia)
PaperCon 2011 Page 646
Nomenclature
• Microfibrillated cellulose (MFC)O i i l- Original name
• Nanocellulose- Collective name for all types of nanocellulose. Used for this material
the last 10 years.- Other nanocelluloses are NanoCrystalline Cellulose (NCC) andOther nanocelluloses are NanoCrystalline Cellulose (NCC) and
Bacterial NanoCellulose (BNC)
• Nanofibrillated cellulose (NFC) = new name started to be used 2• Nanofibrillated cellulose (NFC) = new name started to be used 2 years ago
PaperCon 2011 Page 647
NFC particle size
NFC width/diameter• TEM imaging: 5 30 nm• TEM-imaging: 5-30 nm• AFM-imaging: 5-30 nm• Solid state NMR: 17 nm• Light scattering: 20 nm
NFC l thNFC length• Indicative length = 100 nm to > 1 m
NFC aspect ratio l/d• Given the above data 5 < l/d < 200
PaperCon 2011 Page 648
Flocculation state characterization(Kerekes 1992)(Kerekes 1992)
Crowding Factor N:
N2
cL
2
N 3
cv d
PaperCon 2011 Page 649
Crowding factor and concentration as a function of aspect ratioof aspect ratio
Lundell, Söderberg and Alfredsson (2011), Annu. Rev. Fluid Mech, 43
PaperCon 2011 Page 650
WHAT DO WE NOW FROM OTHER AREAS?
PaperCon 2011 Page 651
What do we know from other areas?
CV=0.05%
PaperCon 2011 Page 652
Shear thinning comparison
0.22%0.14%0.14%0.06%0.14% (mod.)Water
PaperCon 2011 Page 653
Shear thinningNanocelluloseNanocellulose
Water
PaperCon 2011 Page 654
Shear thinning comparison
0.22%0.14%0.14%0.06%0.14% (mod.)Water0.25% NFC0.25% NFC
PaperCon 2011 Page 655
WHAT ABOUT HIGHER FLOW-RATES?
PaperCon 2011 Page 656
Measured pressure lossLong fibre chemical pulpLong-fibre chemical pulp
50
1020
]
2
5
00m
pip
e]
Water
0.5
1
p [m
H20
/10
0 1 0 2 0 5 1 2 50.1
10
0.2p
0.1 0.2 0.5 1 2 5 10U [m/s]
PaperCon 2011 Page 657
Effect of fibresOn relative liquid phase dissipationOn relative liquid-phase dissipation
onA = aspect ratio and FBK = Fully Bleached Kraft pulp
diss
ipat
iod
phas
e d
ve li
quid
Rel
ativ
Volume concentration CVolume concentration, Cv
Bennington & Mmbaga, 12th Fundamental Research Symp. 2001
PaperCon 2011 Page 658
Turbulent spectrum
By definition the turbulent kinetic energy k is the integral of E() over all wavenumbers
log E()
DissipationEnergy ( )k E d
Dissipation rangeInertial
subrangecontaining
range0
log Wavenumber = 2 /l gWavenumber = 2/l where l is the eddy size
PaperCon 2011 Page 659
Visualization technique
Vortical structure in the
PlateletsD ≈ 5µm
flow
µ
• Structures in the flow are visualized by Iriodin particles• The flow is filmed by a digital camera
Reflected light• The flow is filmed by a digital camera• Analysis of captured images can provide data of the flow
condition and structure sizeI id t li htIncident light
PaperCon 2011 Page 660
Turbulent decay
Iriodin particles are added to visualize flow structuresIriodin particles are added to visualize flow structures
Water
PaperCon 2011 Page 661
Turbulent decayFibres strongly modify turbulenceFibres strongly modify turbulence
Iriodin particles are added to visualize flow structures
With 0.2% NBSKWithout pulp
PaperCon 2011 Page 662
Measured pressure lossLong-fibre chemical pulpLong fibre chemical pulp
50
1020
]
2
5
00m
pip
e]
Water
0.5
1
p [m
H20
/10
0 1 0 2 0 5 1 2 50.1
10
0.2p
0.1 0.2 0.5 1 2 5 10U [m/s]
PaperCon 2011 Page 663
Measured pressure loss
0.14%0.14% (mod.)Water
PaperCon 2011 Page 664
Turbulent spectrum
By definition the turbulent kinetic energy k is the integral of E() over all wavenumbers
log E()
DissipationEnergy ( )k E d
Dissipation rangeInertial
subrangecontaining
range0
log Wavenumber = 2 /l gWavenumber = 2/l where l is the eddy size
PaperCon 2011 Page 665
Conclusions
• NFC will probably (at least so some degree) behave as other elongated nano-particleselongated nano-particles
• Maybe some characterstics from non-nano fibre suspensions (pulp) will also be present?S ff f• Strong effect of concentration in various processes- Pumping- Mixingg- Fractionation- Dewatering- Drying- Drying
• All data seem to show shear thinning behaviour = good!• New material forming processes needed!
PaperCon 2011 Page 666